Genetics Flashcards
Codominance
Multiple alleles are simultaneously expressed.
Ex: ABO blood types
Incomplete Penetrance
Individuals who carry mutant genotype but do not express it
Ex: BRCA1
Variable Expressivity
Variability in a phenotype
Ex: NF1
Pleiotropy
One gene is responsible for many manifestations
Ex: Homocystinuria
Anticipation
The tendency of disease to occur in earlier in each generation.
Ex; Huntington
Loss of Heterozygosity
tumor suppression genes must be mutated on both chromosomes to cause cancer.
Ex: Rb
Germline Mosaicism
Multiple distinct cell lines in the gametes, but not somatic cells
Somatic Mosaicism
Gametes are normal, but somatic cells are affected.
Locus Heterogeneity
The same phenotype can be caused by mutations at different genes.
Ex: Albinism
Allelic Heterogeneity
The same phenotype can be caused by different mutations within the same gene.
Ex: B Thalassemia
Heteroplasmy
Presence of both mutated and normal mitochondrial genomes within the same cell.
Impriniting
Methylation of cytosine by SAM
Can cause disease if there is a mutation in the opposite chromosome
Ex: Prader-Wili/Angelman Syndrome
Prader-Wili Syndrome
Chromosome 15
PWS gene from father is mutated or deleted
Obesity, hyperphagia, ID, hypogonadism, hypotonia, temp instability
Angelman Syndrome
Chromosome 15
Maternal UBE3A gene is normally actived but is deleted in this syndrome.
Inappropriate laughter, ID, seizures, ataxia
Uniparental Disomy
Two copies of the same chromosome are inherited from the same parent.
Features of autosomal dominant disorders
Male to male transmission
Skewed lyonization
XXd but the healthy X becomes a bar body so the carrier state is converted to a disease state.
Achondroplasia
FGFR3 Mutation chondrocyte proliferation impairment most common cause of dwarfism 85% due to sporadic mutation (advanced paternal age) 15% autosomal dominant
Acute Intermittent Porphyria
Autosomal Dominant
Mutation is porphobilinogen deaminase
Abdominal pain, neuropathy, psych issues
Increased urinary porphobilinogen
NF1
Autosomal dominant
Chromosome 17
Cafe au lait spots, freckles, Lisch nodules, pheochromocytoma, and optic pathway gliomas.
Variable expression but 100% penetrance
von Hippel Lindau
VHL gene on chromosome 3. Autosomal dominant.
RCC, hemangioblastoma. and pheochromocytoma.
Try hunting for my fragile eggs
Trinucleotide repeat mnemonic Huntingtons Friedreich ataxia Myotonic dystrophy Fragile X syndrome
Huntington
Autosomal dominant CAG repeats (glutamine) basal ganglia atrophy decreased Ach, GABA increased dopamine
Friedreich Ataxia
Autosomal Recessive GAA repeat (GAit Ataxic) Mitochondrial dysfunction Neurologic deficits, DM, cardiomyopathy
Myotonic Dystrophy
Autosomal Dominant
CTG (Cataracts, Tired Muscles, Gonads)
Myotonin protein kinase deficiency
Fragile X Syndrome
X linked dominant
CGG (Chin, Gonads, Gene silencing)
Long face, long jaw, neurpsych problems, joint hyperlaxity, macroorchism
Most common cause of inherited ID
William Syndrome
Microdeletion on chromosome 7
Elfin face, very friendly, intellectual disability
DiGeorge’s Syndrome
Microdeletion on chromosome 22
CATCH-22
Cleft palate, abnormal facies, hypertelorism/T cell deficiency, cardiac defects, hypocalcemia
Histone molecules
H2 H3 H4 are the core, H1 is outside the core and binds the linker DNA.
Polygenic inheritance
Androgenetic alopecia, epilepsy, glaucoma, HTN, ischemic heart disease, schizophrenia, DM2
TTN gene
Titin gene
hereditary dilated cardiomyopathy
Autosomal dominant but incomplete penetrance
